In order to make the operation of fuel dispensers as trouble-free as possible, the most recent designs to a very great extent make use of automatic control arrangements which permit the proper control of a fuel dispensing cycle simply by removing the fuel-dispensing nozzle from its support or housing and, after a desired amount of fuel has been dispensed, replacing the fuel-dispensing nozzle onto its support or into its housing. Known fuel dispensers make use of an automatic clearing or resetting arrangement for the price and volume indicators of the price calculating arrangement of the fuel dispenser; the resetting arrangement always resets the indicators when the dispensing nozzle is removed from its support or housing. In response to the completion of the resetting of the digit rollers of the volume and price indicators, a switch is activated by means of a connecting arrangement incorporating gearing, and activation of such switch results in the supply of operating current to the motor of the pump of the fuel dispenser. After the desired amount of fuel has been dispensed, the fuel-dispenser pump motor is, again automatically, turned off when the dispensing nozzle is replaced upon its support hook or returned to its support housing.
For the automatic resetting of the price calculator of the fuel dispenser it is already known to employ an electromechanical resetting arrangement incorporating an electrical drive motor for causing the resetting operation to be performed. German published patent application No. 1,212,752 discloses an automatic arrangement for controlling the resetting operation of the price calculator of the fuel dispenser and for initiating and terminating operation of the motor of the pump of the fuel dispenser; in this known arrangement a cam disk is driven by the resetting motor of the price calculator and controls an electrical multiple switch. This multiple switch, on the one hand, together with a main switch activated by the dispensing nozzle, controls the resetting motor, and, on the other hand, controls the relay winding of a relay device whose relay switch turns the motor of the pump of the fuel dispenser on and off.
This known control arrangement has the disadvantage that the resetting of the price calculator is not necessarily completed, in the event the dispensing nozzle is only briefly removed from its support and then almost immediately replaced. As a result, the resetting of the digit wheels of the price calculator can be interrupted by the operator of the fuel dispenser, simply by removing the dispensing nozzle from its support and then quickly replacing it; if the dispensing nozzle is replaced quickly enough, before the resetting of the digit wheels is completed, a combination of digits can appear on the digit wheel arrangement corresponding neither to an amount of fuel which has actually been dispensed nor to the number zero. In order to preclude the performance of computations based upon meaningless values, such as could result in the manner just described, it is necessary to preclude the possibility of interrupting the resetting of the digit wheels. Indeed, with this known construction, the rotating control structure can be stopped at any desired point in the cycle of rotating thereof, i.e., either during the first portion of the cycle during which the price calculator is reset, or else during the second portion of the cycle which is required for turning off the pump motor and for preparing the arrangement for the next resetting operation. Furthermore, with this known construction, there is no guarantee of an avoidance of damaging overlaps in the energization of the resetting motor and the energization of the pump motor, since with the multiple switch merely the working winding of the pump motor switch is controlled. The actual state of energization of the pump motor--i.e., whether or not the pump motor is energized--relative to the state of energization of the resetting motor is simply not determined, and accordingly a direct interdependence between the energization of the two motors does not exist.
U.S. Pat. No. 3,216,659 discloses another electromotor-driven resetting arrangement. In this arrangement, the initiation of the resetting operation is effected by means of a manually activated lever connected to a rotary switch. When the lever is moved to activated position, it becomes mechanically locked in such position, and remains locked until the resetting operation has been completed, whereupon the pump motor of the fuel dispenser is turned on. This locking of the manually activated control lever at the start of the control cycle for the resetting operation is accomplished by means of a cooperating series of mechanical components, and furthermore the control lever actually activates the electrical switch for the resetting motor only through the intermediary of numerous mechanical coupling elements. The mechanical locking of the manually activated control lever used to initiate the resetting operation is caused to terminate by a quite complicated gearing mechanism which is operative upon completion of the resetting operation for releasing a locking member in the counting mechanism and which is furthermore operative for connecting the pump motor circuit to power. Furthermore, when the manually activated control lever is released from its locked position and permitted to return to the non-activated position, the actual deactivation of the resetting motor and the pump motor switch is very indirect, being accomplished through the intermediary of a plurality of mechanically driven control cams and catch devices which cooperate and move relative to each other in a predetermined succession in order to move the control switches for the resetting motor and for the pump motor switch to the deactivated positions. The complexity of the mechanical components and control elements is very great, and furthermore proper cooperation between these mechanical components and control elements in the correct order with the correct relative timing makes it very difficult to perform adjustments upon the mechanisms. Also of disadvantage is the fact that the locking of the manually activated lever does not occur directly by means of the pump motor itself, and also the turning off of the pump motor again can be performed only by way of the manually activated mechanism mounted on the price calculator. For these reasons, this arrangement is furthermore not suited for remote control of the price calculator.
Another known construction provides, for the turning on of the pump motor, a switch additionally provided with an interruptor contact for turning off the resetting motor. This switch is controlled by a cam disk driven by a one-revolution clutch. The cam disk activates a sliding member which through the intermediary of a further coupling member brings the switch into the turn-on position for the pump motor. Finally, the switch is maintained in such turn-on position by means of an additional locking device. It is desired that the cam disk, after disengagement of the one-revolution clutch and the turn-off of the resetting motor, be reliably turned further beyond its switching position so as to later block return of the aforementioned sliding member to its starting position; to this end, there is provided a second cam disk rigidly connected with the first cam disk. A biasing spring forwardly biases such second cam disk in order to cause the switch to be pushed to the blocking position just mentioned. The second cam disk has no influence upon the turning on of the motor switch; however, it is necessary for the release of the turn on mechanism and to make possible the turning off of the switch.
With this construction, the turning off of the pump motor is effected by reversing the control switch, thereby briefly connecting to the motor current path an electromagnet which pulls the locking element for the pump motor turn-on into the proper position.
This known construction, likewise, involves great mechanical and electromechanical complexity. Also, it lacks the indispensable safety measure in question, namely that a resetting operation, once initiated, cannot be interrupted. Furthermore, the circuit of the second functional phase can only effect a turning off of the pump motor and simultaneously of the control circuit producing this effect. Accordingly, it is not adapted for the control of a second control cycle which occurs in response to the termination of the dispensing of fuel and involves the performance of peripheral functions, such as the printing of a receipt by a printing mechanism, and the like.
Especially in the case of self-service and coin-operated fuel dispensers, the fuel dispenser should be so designed that the customer, after he fills up his fuel tank to the desired extent, is automatically given a printed receipt, without the customer having to perform any additional manipulative steps to cause such receipt to be printed and dispensed, and with the modes of operation of the various mechanisms involved being such as to preclude malfunction, especially of the type described earlier, namely interruption of the resetting operation. For printing the receipt, dispensing the receipt and then causing the receipt printer to become reset, use should be made of the control motor which is anyway present for the purpose of resetting the indicators upon removal of the dispensing nozzle from its support. However, for the control of the printer, the electrical control motor can be employed in a separate second control cycle occurring after the dispensing of fuel has been terminated. For example, this second control cycle should start automatically when the fuel dispensing nozzle is replaced onto its support, and such second control cycle should proceed to completion and not be interrupted or influenced by external manipulations such as manipulation of the support for the fuel dispensing nozzle, or the like. These requirements cannot be achieved with the known arrangements for the reasons explained above.
U.S. Pat. No. 3,447,719 discloses another arrangement for controlling the resetting motor and the pump motor in a fuel dispenser. In that arrangement, the resetting motor drives a control shaft in two discrete half-revolutions. Provided on the control shaft are a plurality of control cams. The control circuit is activated during a first half-revolution of the output shaft of the resetting motor by means of switches controlled by two cams and by means of a further switch controlled by the dispensing-nozzle support hook. During this first half-revolution, the resetting operation is performed and the winding of the pump motor switch is energized, in turn connecting the pump motor, which is arranged in a separate current path, to a current supply.
A disadvantage of this arrangement is that the control circuit requires the use of several switches whose activations must be properly timed by means of control cams. These switches are controllable only separately, making necessary various mechanical control means and the separate arrangement of the switches. Furthermore, the electrical circuit connections which can be established and disestablished by means of the switches, on account of the type of switches employed, can only be established indirectly through the force of magnetic attraction. The control components are expensive, and so are the considerable number of switch devices required, since the switches must be provided with explosion-preventing means. Furthermore, a direct dependence between the current-carrying condition of the control motor and of the pump motor does not exist, so that undesired overlaps in the energization of the two motors, such as can lead to damage of the arrangement, are not absolutely avoided. For example, the switch activated by the support hook for the dispensing nozzle may be activated to thereby close the current path for the control motor but then during the transition into the self-locking state the current path may become interrupted. Only by making the moving parts involved of sufficiently great mass, and thereby of sufficient inertia, can the currentless condition of the circuit for the control motor be overcome, until finally the corresponding holding circuit is closed. This defect, even when the moving parts involved exhibit only a low resistance to movement, can sometimes result in the entire mechanism coming to a stop.